This code is designed to be small, fast, and accurate to within ±1 arcminute. It is based on the authoritative and well-tested models VSOP87 and NOVAS C 3.1.

Rigorously unit-tested against NOVAS, JPL Horizons, and other reliable sources of ephemeris data.

Features

Provides calculations for the Sun, Moon, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.
Calculates for any calendar date and time between the years 1600 and 2200.
Provides heliocentric and geocentric Cartesian vectors of all the above bodies.
Determines apparent horizon-based positions for an observer anywhere on the Earth, given that observer's latitude, longitude, and elevation in meters. Optionally corrects for atmospheric refraction.
Rise, set and culmination times of Sun, Moon, and planets.
Date and time of Moon phases: new, first quarter, full, third quarter (or anywhere in between as expressed in degrees of ecliptic longitude).
Finds equinoxes and solstices for a given calendar year.
Finds apparent visual magnitudes of all the supported celestial bodies.
Predicts dates of planetary conjunctions and oppositions.
Predicts dates of Venus' peak visual magnitude.
Predicts dates of maximum elongation for Mercury and Venus.

Supported Languages

JavaScript

API Reference

C/C++

(Coming soon.)

Go

(Coming soon.)

Python

(Coming soon.)

Languages

C 23%

JavaScript 15.9%

C# 14.2%

Python 11.1%

HTML 10.2%

Other 25.6%